Figure 2-2. Quartz sand grains (Q) at stylolites (red arrows) along which accumulation of silt-sized quartz is shown in an other image. Note the smooth rounded edges of these grains away from the styloites (small black arrows) and the pressure-dissolved serrate grain margins at the stylolites (large arrows). Evidence like this confirms that stylolite development is indeed a process in which rock material is removed in solution rather than compacted by a ductile mechanism. Also note how the large quartz grain at right holds apart two small stylolites that merge to the left and right.

      Photomicrograph was taken in plane-polarized light; field of view is 2.4 mm wide. Roadcut on US 322 bypass outside State College, Pennsylvania; Sample PA4-2; thin section S-1-146. Sample collected by L. Bruce Railsback.

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